Look about halfway down this page under “blueprints"
[COLOR=#800080]http://www.projectrho.com/SSC/model.html[/COLOR] and you'll find the probable inspiration for the defiant? Just take away the nosecone, "neck" and "wings" of the Leif Ericson and you've basically got the defiant design. At any rate, this is probably a good place to start on a TOS era defiant.